1. The Field of the Invention
The present disclosure relates generally to a method for producing steel, and more particularly, but not necessarily entirely, to a method for producing liquid steel from iron ore which may or may not be supplemented with scrap steel.
2. Description of Related Art
In the conventional steel making processes, iron ore is reduced to a metallic state by carbon monoxide and fusion reduction in a highly carbonized environment. This occurs in both blast furnace and Corex processes (defined below). A blast furnace is a towering cylinder lined with heat-resistant (refractory) bricks used by integrated steel mills to smelt iron from its ore. Its name comes from the “blast” of hot air and gases forced up through the iron ore, coke and limestone that load the furnace. Under extreme heat, chemical reactions among the ingredients release the liquid iron from the ore. The blast of air burns the coke, and limestone reacts with the impurities in the ore to form a molten slag. The hot metal collects in the bottom of the furnace. Once fired up, the blast furnace operates continuously.
The Corex process is a coal-based smelting process that yields hot metal or pig iron. The process gasifies non-coking coal in a smelting reactor, which also produces liquid iron. The gasified coal is fed into a shaft furnace where it removes oxygen from iron ore lumps, pellets or sinter. The reduced iron is then fed to the smelting reactor.
The environment in the blast furnace and the Corex processes produces an iron with carbon levels in the liquid iron far above the desired level for quality crude liquid steel. This results in conditioning the liquid iron such that it is susceptible of harboring other impurities. Both these methods require other unit operations to remove these impurities and excessive carbon. Expensive processes, such as the Bessemer Convertor, Open Hearth Furnace and the Electric Furnace have been developed in which expensive equipment and operations, including the basic oxygen processes, are used for the purpose of removing these undesirable impurities to acceptable levels. These operations are expensive, consume great quantities of energy, and have limitations as to the amount of the various impurities they can economically remove and the quality and types of steel each can produce.
Because of the production processes and the nature of the carbonaceous iron produced in the blast furnace and Corex processes, virtually all the phosphorous constituents that enter the furnace are reduced, and readily combine chemically with the ferrous metal which is drawn off in solution with the liquid metal as an impurity. Phosphorous is very detrimental to the metallurgical properties of steel, which with present customary methods is difficult and expensive to remove, and results in losses of metals that must be oxidized into the slag bath to aid in the removal of this highly detrimental impurity. The removal of phosphorous results in the loss of metallic iron. Because of the excessive carbonaceous environment in the combustion zones of both of these processes, only primary combustion occurs. Primary combustion may be referred to as the combustion of carbon and oxygen to form carbon monoxide. Primary combustion may utilize only a mere 28% of the potential energy available from the complete oxidation of carbon. When the secondary phase of the oxidation of carbon is completed, the calorific energy released elevates temperatures and fusion reduction, which absorbs high levels of energy and proceeds more rapidly with higher temperatures when controlled portions of carbon and oxygen are being fed into the process.
The present process may release all the potential energy that can be released from the oxidation of carbon. Furthermore the process can reclaim a larger portion of the energy released if it is not utilized in the fusion and reduction process. Various volumes of carbon dioxide or carbon monoxide may serve as oxygen carrying vehicles to remove oxygen from the process. Carbon monoxide may be used as an export gas or it may be utilized for the production of hydrogen gas.
The process of the present disclosure may utilize virtually all the secondary combustion (the combustion of carbon monoxide and oxygen to form carbon dioxide) of carbon in the fusion reduction process and may be extremely more fuel efficient and less capital extensive than methods now in use. Also, the process may be very flexible in the quantities of scrap steel that can be utilized. This may be beneficial due to the variations in the availability of scrap and the quality of steel desired. The present process may readily reduce high phosphorous fine low cost ores to crude liquid steel. It may also lower considerably the cost of maintenance, and require far less fuel and man hours to produce a given quantity of steel. Moreover because the levels of impurities can be readily lowered and removed, in some instances becoming by-products, the present process may be more cost efficient and the products more desirable. The present process can produce a quality of crude liquid steel of high purity ready for alloying, casting or further processing.
The prior art is thus characterized by several disadvantages that are addressed by the present disclosure. The present disclosure minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.
The features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.